Explosive detection screening system

ABSTRACT

An explosive detection screening system used for the detection of explosives and other controlled substances such as drugs or narcotics. The screening system detects the vapor and/or particulate emissions from the aforementioned substances and reports that they are present on an individual or object and the concentration of each substance detected. The screening system comprises a sampling chamber for the collection of the vapor and/or particulate emissions, a concentration and analyzing system for the purification of the collected vapor and/or particulate emissions and subsequent detailed chemical analysis of the emissions, and a control and data processing system for the control of the overall system.

This application is a continuation of copending application Ser. No.447,724 now U.S. Pat. No. 4,987,767, which is a continuation-in-part, ofapplication Ser. No. 364,663, filed Jun. 9, 1989 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to systems for the detection of explosives andother controlled substances such as drugs or narcotics. Moreparticularly, the present invention relates to an integrated systemconsisting of a sampling chamber, a detection system, and a dataprocessing system, for the detection of the vapor and/or particulateemissions of explosives and controlled substances in a non-invasive

2. Discussion of the Prior Art

In recent years there has been a steady increase in the illegal use ofexplosives as well as an increase in the transportation of contrabandsubstances such as drugs or narcotics. It is impossible to detect theexistence or prevent all of the cases of bombings and drug smugglinggoing on; however, it is possible to detect explosives and contrabandsubstances in particular areas where high visibility and/orvulnerability exists such as in airports or airplanes. There arenumerous ways in which an individual can place drugs or explosives on anairplane, and even more places an individual can hide the drugs orexplosives once on the airplane. The illegal substances can be broughton the airplane by a knowing or unknowing individual by concealing thesubstance on his/her person or by placing the substances in baggage tobe placed in the cargo section of the aircraft.

The methods for detecting substances such as explosives and drugs ornarcotics have been studied for many years, and various techniques havebeen developed which range from explosives/drug sniffing dogs to highlysophisticated vapor detection devices. Basically, the detection of theaforementioned substances is accomplished in one of two ways; namely,non-vapor detection and vapor detection. Non-vapor detection methodsinclude x-ray detection, gamma-ray detection, neutron activationdetection and nuclear magnetic resonance detection. These methods ofdetection are more applicable to the detection of the various substanceswhen the substances are concealed and are carried or associated withnon-living items such as baggage to be carried onto an aircraft in thatthe detection techniques might pose a threat to living items. Vapordetection methods include electron capture detection, gas chromatographydetection, mass spectroscopy detection, plasma chromatography detection,bio-sensor detection and laser photoacoustic detection. These methods ofdetection are more applicable to the detection of substances that areconcealed and associated with living items such as those that can becarried by individuals including the residuals left on the individualwho handled the various substances. All of the above methods arepresently utilized, including explosive and drug sniffing dogs.

Today, there are many private and government research studies devoted tothe development of systems and methods for the detection of explosivesand drugs or narcotics. With the advances in explosives technology, suchas the advent of the plastique explosives, which can be disguised ascommon items, it is becoming increasingly difficult to detect thesesubstances. The problems that must be overcome in the detection of thesesubstances as well as others, include low vapor pressure of theparticular vapors escaping from the particular substance, the searchtime and the throughput of the various systems, the low concentration ofvapor or particulate emissions from the particular substance, isolationof the particular substance with a high degree of reliability, andmaintaining the integrity of the systems environment.

There is numerous prior art dealing with the technology of explosive anddrug detection devices. The article "Air Flow Studies For PersonnelExplosive Screening Portals" authored by R. L. Schellenbaum of ScandiaNational Labs which was published in 1987 as part of the CarnahanConference on Securities Technology in Atlanta, Ga. (Jul. 15, 1987)discloses a study on various types of integrated systems for thedetection of contraband explosives The study outlined a three stepprocess, which includes the collection of vapor, preconcentration, anddetection, for the capture and detection of the vapors emanating fromexplosive substances. The article discloses various types of collectiondevices for collecting the sample. Various portal configurations and airflow mechanics within each of the portals were studied to see which oneprovided the best sample. The Atmos-Tech Air Shower Portal, a ModifiedAtmos-Tech Portal and a Cylindrical Portal were used in the study withvarious air flow configurations. The study concluded that downward,semi-laminar flow over the body cross-sectional area combined with avacuum flow collection funnel of approximately twelve inches in diameterplaced beneath the grating in the floor of the portal was the best wayto collect the explosives vapor or particulate emissions from anindividual passing through the portal.

For the detection part of the study, various detection devices were usedincluding the Phemto-Chem 100 Ion Mobility Spectrometer in combinationwith a preconcentrator developed by Ion Track Instruments Inc. The ionmobility spectrometer is a plasma chromatograph which uses anatmospheric ion-molecular reactor that produces charged molecules whichcan be analyzed by ion mobility. The preconcentrator comprises amotor-driven, metal screen disc rotated with a cast metal casing. Thescreen adsorbs the vapor and is then heated for desorption of the vapor.This adsorption-desorption process is the necessary preconcentrationstep which is used to increase the vapor and/or particulateconcentration in the collected air sample.

The major problem encountered in the use of the portal detection systemsin the study was maintaining the integrity of the sample air volume. Inmaintaining the integrity of the sample air volume, it is necessary toprevent the sample air volume to be contaminated with the ambientenvironment at the same time trying to maintain a steady flow of trafficthrough the portal, which is essential to efficient operation of anytype of screening system in which heavy traffic is common place. Theaforementioned article suggests that the integrity of the sample airvolume was not maintained in portals without doors. If ambient draftswere present, such as those from air conditioners or just the flow ofpedestrian traffic, a reduction of ten percent in detection wasencountered. The addition of doors on the portals effected a rise in thedetection rate; however, it produced unacceptable pedestrian trafficproblems which would not meet the requirements for high throughputsrequired by airports.

In the patent art, there are a group of references which disclosevarious methods and devices for detecting contraband substances,including both drugs and explosives. These references are all directedto the detection of contraband substances within a container or luggage,and not those carried on a person. U.S. Pat. No. 4,580,440 and U.S. Pat.No. 4,718,268 both assigned to British Aerospace Public Company Limiteddisclose a method and apparatus for detecting contraband substancessealed in freight type cargo. Basically, the method consists of sealingthe cargo in a container, agitating the cargo in order to shake off thevapor or particulate matter emanating from the cargo into thesurrounding atmosphere, sampling the atmosphere, heating the collectedsample and analyzing the sample utilizing gas chromatography. U.S. Pat.No. 4,202,200 assigned to Pye Limited discloses an apparatus fordetecting explosive substances in closed containers. Basically, objectssuch as luggage are passed through a controlled axis tunnel wherein theobjects are swept by circulating air flows, and then the air sample iscollected and analyzed. It is also suggested that if a larger tunnel isconstructed, people as well as objects can be passed through it. Theaforementioned inventions provide a means and method for detectingcontraband substances by using vapor sampling; however, none of theinventions provide or suggest the use of a preconcentrator means forincreasing the sensitivity and selectivity of the detection means.Additional patent references which disclose similar type systems areU.S. Pat. No. 3,998,101 and U.S. Pat. No. 4,111,049.

There are numerous patent references in the testing and monitoring artwhich disclose a concentration step which includes the filtration orabsorption of the molecules of interest over time. After a predeterminedperiod of exposure, the filtering/absorption media is removed anddesorbed with heat, while a new filter/absorption media is placed in theair stream. U.S. Pat. No. 3,768,302 assigned to Barringer ResearchLimited discloses a system used in the geological testing area and inwhich the system receives an air stream containing particulates. Thesample undergoes a concentration step which includes passing the airsample over two paths with adsorbing/desorbing steps, and finallyanalyzed. U.S. Pat. No. 4,056,968 assigned to the same assignee as theabove patent also discloses a system which is also used in thegeological testing area. In this invention, the concentrated moleculescould be desorbed from a moving tape as well as from a moving disk. U.S.Pat. No. 4,775,484 discloses a rotating filter media which is used toabsorb particulate material during one stage of its rotation, and whichis purged or cleaned at a separate and second stage of its rotation.U.S. Pat. No. 4,127,395 also discloses a common absorption/desorptioncircuit using a pair of absorbent media, wherein one of the pair isabsorbing, while the other is desorbing. U.S. Pat. No. 3,925,022, U.S.Pat. No. 3,997,297 and U.S. Pat. No. 3,410,663 all discloseabsorption/desorption type devices. All of the aforementioned devicesdisclose systems for the absorption and subsequent desorption ofparticulate or vapor matter; however, none disclose a portal typesampling chamber.

SUMMARY OF THE INVENTION

The present invention is directed to a system for the detection ofexplosives, chemical agents and other controlled substances such asdrugs or narcotics by detecting their vapor and/or particulateemissions. The system comprises a sampling chamber, a vapor orparticulate concentrator and analyzer, and a control and data processingsystem. The system is particularly useful in field environments, such asairports, where it can be used to detect the aforementioned substanceson an individual or in the baggage of the individual. The system meetsthe requirement to detect the aforementioned substances in anon-invasive manner at any required level, and to do it so quickly thatthe free passage of people and baggage is not unduly interrupted.

The sampling chamber is a portal with internal dimensions ofapproximately six feet in length, seven feet in height and three feet inwidth. The dimensions of the portal are such as to allow an averagesized individual as well as a wheel chair bound individual to easilypass through. The portal is designed in such a way as to have aninternal air flow sweep over an individual walking or passing throughthe portal at a normal walking pace, and at the same time have the airsample swept from the individual contain a meaningful concentration ofvapors or particulate matter to be analyzed. To accomplish this, thesampling chamber or portal is designed with a unique geometry andcontains air guides or jets for providing an air flow which effectivelyisolates the internal air volume from the ambient environment whileefficiently sweeping the individual passing through the portal. The airvolume or sample inside the portal is collected through a sampling portlocated within the ceiling section of the portal. The air sample is thentransported to the sample collector and preconcentrator (SCAP).

The sampling chamber or portal is capable of collecting and deliveringto the SCAP vapor and/or particulate matter when they are present in aslow a concentration as several parts per trillion of ambient air. TheSCAP, through a series of steps of decreasing sample volume andincreasing sample concentration, delivers a concentrated sample to afast response chemical analyzer which may be either a gaschromatograph/electron capture detector or an ion mobility spectrometeror both. The principle of operation of the SCAP is one of adsorbing thesample onto a selected substrate with subsequent selective thermaldesorption. This process is repeated through a series of steps ofdecreasing sample volume and increasing sample concentration. Uponcompletion of the preconcentration steps, the purified sample materialis analyzed by the aforementioned devices wherein the analysis consistsof identifying the various materials and determining the amount ofmaterial present.

The total system and all system processes are controlled by a controlsystem which comprises a digital computer and associated software. Thesystem is configured and controlled to make all required measurementsand prepare the results in a usable and intelligible format. The controlsystem controls the collection of vapors, the preconcentration andanalysis steps, and the data analysis and data formatting. In addition,the computer continuously performs self diagnostic and self calibrationprocedures on the total system and alerts the user to any potentialproblems.

The system for the detection of explosives and other controlledmaterials of the present invention provides for the efficient detectionof explosives, chemical agents or other controlled materials such asdrugs or narcotics by detecting the vapor and/or particulate emissionsfrom these substances. The vapor or particulate emissions can come fromsubstances concealed on the individual, the individual's baggage, orfrom a residue left on an individual who handled the particularsubstance. The present invention provides a system with a high degree ofsensitivity and selectivity to a wide range of substances. The highdegree of sensitivity and selectivity is accomplished by employing asystem which utilizes the combination of a unique geometry portal withaerodynamics that prevent the cross-contamination of air within theportal with that of the ambient environment and a multi-stagepreconcentrator that decreases sample volume while maximizing sampleconcentration thereby allowing much larger sample volumes to be taken aswell as much shorter sample collection times. The system provides a highreliability rate which is accomplished by utilizing the computer controlsystem for automatic calibration and self diagnostic procedures. Inaddition, the system provides a high degree of versatility in that bychanging the programming of the computer, a wide range of explosives,controlled chemical agents, and drugs and narcotics which have differingphysical and chemical properties can be detected. Having the totalsystem under software control provides a more versatile system and onethat is easily reconfigurable.

The present invention has a wide variety of applications where a highthroughput of people is required. In airports, the detection ofexplosives and controlled substances is of paramount importance due tothe rise in terrorist attacks and drug smuggling. The present inventionallows for the fast and reliable detection of the aforementionedsubstances in a non-invasive manner in a variety of field environmentssuch as in airports. The system of the present invention is applicablewhere the detection of concealed substances is absolutely required.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, there is shown thedrawings the forms which are presently preferred; however, it should beunderstood that the invention is not necessarily limited to the precisearrangements and instrumentalities here shown.

FIG. 1 is a sectional side view of the sampling chamber of the presentinvention;

FIG. 2 is a sectional end view of the sampling chamber of the presentinvention taken along section lines 2--2' in FIG. 1;

FIG. 3 is a top view of the sampling chamber of the present invention;

FIG. 4 is an end view of the sampling chamber of the present invention;

FIG. 5 is a diagrammatic representation of the flow of air within thesampling chamber of the present invention;

FIG. 6 is a diagrammatic sectional view of the internal/external airboundary that exists at the end of the sampling chamber of the presentinvention;

FIG. 7 is a diagrammatic block diagram of the sample collector andpreconcentrator of the present invention.

FIG. 8 is a diagrammatic block diagram of the sample collector andpreconcentrator of the present invention with a three filterconfiguration;

FIG. 9 is a plane view of the three filter configuration of the primarypreconcentrator of the present invention.

FIG. 10a is a diagrammatic representation of the multi-port valve usedin the present invention with the valve in the load position;

FIG. 10b is a diagrammatic representation of the multi-port valve usedin the present invention with the valve in the inject position;

FIG. 11a is a diagrammatic diagram of the portable sample collector ofthe present invention;

FIG. 11b is a diagrammatic representation of the luggage sampling meansof the present invention;

FIG. 12a is a diagrammatic representation of the particulate collectorand detector means of the present invention utilizing a six-port valveconfiguration;

FIG. 12b is a diagrammatic representation of the particulate collectorand detector means of the present invention utilizing a three-way valveconfiguration;

FIG. 13 is a block diagram of the control and data processing system ofthe present invention;

FIG. 14a is a flow chart of the computer program used in the presentinvention utilizing a six-port valve configuration for the particulatecollector and detector means;

FIG. 14b is a flow chart of the computer program used in the presentinvention utilizing a three-way valve configuration for the particulatecollector and detector means; and

FIG. 15 is a time chart indicating the various time durations of theprocesses associated with the screening process.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The explosive detection screening system of the present invention isdesigned to detect explosives, chemical agents or other controlledmaterials such as drugs or narcotics by detecting their vapor orparticulate emissions. These substances are assumed to be concealed onindividuals or in their baggage in airports or in other highvulnerability, high visibility environments. It is necessary to detectthese substances in a non-invasive manner at any required level, and todo it so quickly that the free passage of people and baggage is notunduly interrupted. The system is an integrated system comprising asampling chamber, a vapor and/or particulate concentrator and analyzerand a control data processing system.

The sampling chamber is a portal in which internally generated air flowssweep the vapor and/or particulate emissions emanating from anindividual or object passing through the chamber to a collection area.The sampling chamber is designed in such a way as to capture a highenough concentration of emissions so as to be able to detect thepresence of the aforementioned substances with a high degree ofreliability and dependability. The internal volume of air isrecirculated with a small amount being removed at the sampling time. Atthe sampling time, an external air pump or fan draws a sample of thecollected air volume into a sample collector and preconcentrator (SCAP).

The sampling chamber is capable of collecting and delivering to the SCAPvapors when they are in as low a concentration as several parts pertrillion of ambient air. The SCAP, through a series of steps ofdecreasing sample volume and increasing sample concentration, delivers aconcentrated sample to a fast response chemical analyzer which may beeither a gas chromatograph/electron capture detector or an ion mobilityspectrometer or both. Using this multi-stage concentration process ofadsorption and desorption, much larger sample volumes can be processedwith high degrees of sensitivity and selectivity. The data collected isthen assimilated and analyzed by a digital computer which is part of thecontrol system which operates and controls the total system.

The control system is a control and data processing system of which theprimary requirement is to report the presence of, and if required, thelevel of a specified substance. The system must be capable ofdistinguishing between background levels of a substance and alarmlevels. The system also controls the operation of the entire system byautomatic control methods which is run by a microprocessor or digitalcomputer. The control system is easily reprogrammed to detect varioussubstances because of modularized programming techniques.

SAMPLING CHAMBER

The sampling chamber for people is a portal that is designed in such away that as a person walks through this chamber, at a normal walkingpace, an internal air flow carries a sample of vapors and/or particulatematter from them to a sampling port where it will be collected foranalysis. There are three major design requirements that the chamber wasdesigned to meet. First, the sampling chamber must gather a meaningfulsample of the environment surrounding a person or object passing throughthe chamber. In considering a solution to the problem posed by the firstdesign requirement, it is necessary to consider that the samplingchamber must be large enough for an average size individual tocomfortably pass through the chamber; therefore, there is a considerablevolume of air located within the chamber resulting in possibly onlyseveral parts vapor or particulate emission per trillion parts of air orpossibly even less. The solution to this problem of dilution is todesign the chamber long enough so the individual or object passingthrough the chamber remains in the chamber for a duration of time so asa meaningful sample of the environment can be gathered. Second, for thepurposes of sensitivity, selectivity and preventing cross-contaminationof the sample to be analyzed, the sample to be collected must beisolated as much as possible from the ambient environment. Inconsidering a solution to the problem posed by the second designrequirement, it is necessary to once again consider the problem ofdilution caused by having a larger chamber. Since there already exists adilution problem, the chamber must be designed with a unique geometryand internal acrodynamics so as to prevent further dilution andcontamination by the mixing of internal air with the ambient air to thegreatest extent possible. The third design requirement is that thesample must be gathered in as complete form as possible in as short astime as possible. In considering a solution to the problem posed by thethird design requirement, it is necessary to consider the problems andsolutions considered above and find a balance between them. The time anindividual or object spends in passing through the chamber must be longenough so as to gather a meaningful sample, but not long enough to causeunduly long pedestrian traffic delays. Secondly, since there is adilution problem, the chamber was designed in a unique way so as toprevent cross-contamination with the ambient environment, and thisunique design must not prevent the normal flow of traffic; therefore,the aerodynamics discussed in the solution to the second problem must besuch that the meaningful sample is gathered quickly.

Referring to FIGS. 1 and 2, there is shown a sectional side view and endview of the sampling chamber 100 or portal. The sampling chamber 100 hasa rectangular geometry having internal dimensions of approximately sixfeet in length, seven feet in height, and three feet in width. Thesedimensions allow an average size individual, walking at an normalwalking pace to remain in the chamber 100 for approximately two to threeseconds which is enough time to gather the aforementioned meaningfulsample. The rectangular chamber 100 has two walls 102a and 102b, whichrun the length of the chamber 100, a floor 104, a convergent orconically shaped ceiling 106 the importance of which will be discussedsubsequently and a roof 107. In order to maintain the uninhibited flowof pedestrian traffic through the chamber 100, no doors and only twowalls, 102a and 102b, were used. Hand rails 108a and 108b attached towalls 102a and 102b respectively are provided to aid individuals inpassing through the chamber 100 quickly and safely. The floor 104 of thechamber 100 is not a necessary component, and in other configurations itis not utilized. The chamber 100 can be constructed utilizing a varietyof materials including aluminum and plastics; however, clear materialssuch as plexiglass or fiberglass is preferred so individuals passingthrough the chamber 100 can be observed. In addition, a video camera 109may be utilized to capture an image of the individual passing throughthe chamber 100 which will be electronically stored along with thecollected data.

The sampling chamber 100 operates on an air recirculating principle andthe only air removed from the internal recirculating volume is acomparatively small amount leaving by sampling port 118a. The internalair volume is circulated through internal air flow guides or jets and iscollected by collection duct 110 which is a 16"×20"×6" rectangular ductconnected to the center of the conical ceiling 106 and which emptiesinto the space created between the ceiling 106 and the roof 107. Thisresults in a large volume of controlled recirculating air flow capableof delivering a vapor and/or particulate sample from anywhere in onesecond.

The conical ceiling 106 aids in the collection of the sample volume bycreating an inverted funnel for the air sample flow which serves toconcentrate a larger volume of air across a smaller cross section forsampling purposes. A dynamic low pressure zone is created in the regionof the collection duct 110 when the air is drawn through the collectionduct 110 into the ceiling plenum by four exhaust fans two of which areshown in FIG. 2 as 114, and 114a. In each corner of the chamber 100,there are six inch diameter end columns 112a-d. Each of the four endcolumns 112a-d are mounted vertically in the chamber 100 and run fromthe floor 104 to the ceiling 106. Each column 112a-d has six slots ofone foot in length and a half inch in width 113a-d as shown in FIG. 3,which is a top view of the chamber 100, with inch and a half internalguide vanes (not shown) for directing the air flow at a forty-fivedegree angle towards the center of the chamber 100 as shown by arrows115a-d in FIG. 3. The air flow through the columns 112a-d is provided byfour independent fans, two of which are shown in FIG. 2 as fans 114 and114a. The four fans are mounted in the chamber 100 above the conicalceiling 106 and below the outer roof 107. Each fan is connected to oneof the end columns 112a-d and provide 1000 CFM of air to each column112a-d resulting in an air velocity of 17 m/sec., in the directionsindicated by arrows 115a-d, from the guide vanes of the columns 112a-das shown in FIG. 3. The suction side of the fans are open to a commonplenum located in the same space that the fans occupy. In addition tothese inwardly directed vertical air jets 113a-d there are two upwardlydirected air guides 117a and 117b or jets located in side air flow pipes116a and 116b which are mounted along the floor 104 and against walls102a and 102b. The side flow pipes 116a and 116b are connected to endcolumns 112a-d and receive air from them. In each side flow pipe 116aand 116b there are twelve inch by half inch air slots 117a and 117blocated in the center of each pipe and directed towards the center ofthe chamber at a forty-five degree angle as shown in FIG. 4. The airvelocity of the air leaving side flow pipes 116a and 116b is 15 m/sec inthe direction indicated by arrows 119a and 119b. The combined effect ofthe air flow created by the end columns 112a-d and the side flow pipes116a and 116b is a dynamic high pressure region created in the centerregion of chamber 100. The recirculating fans which draw air throughcollection duct 110 create a dynamic low pressure zone within chamber100, which creates a net air flow up towards the collection duct 110.This air flow is the flow that sweeps individuals or objects passingthrough the chamber. The effect of the high pressure region and the lowpressure region created by the exhausting of the air sample throughconical ceiling 106 and into the collection duct 110 is a balance ofatmospheric conditions which results in very little external airentering or leaving the chamber 100. Basically, the high pressure regioninhibits air from entering the chamber 100. The majority of the movingair mass goes through the collection duct 110 and to the common plenumwhere it will once again be used by the four fans to recirculate theinternal volume of the chamber 100. A portion of the recirculated air iscollected through a sampling port 118a, which is the open end of astainless steel pipe 118 which is used to transport a selected samplefrom the chamber 100 to the second stage of operation; namely, thepreconcentration stage which shall be discussed subsequently.

The four end columns 112a-d and the two side air flow pipes 116a and116b represent one embodiment for delivering the air supplied by thefour independent fans as separate and directional air jet streams. Thefans can be connected to various types of air ducts or plenums withguide vanes or nozzles to form the exiting air into jet streams. Inaddition, partitioned hollow walls also with guide vanes or nozzles canbe used as an alternate approach for forming the air from the fans intoseparate and directional air jet streams. The manner in which the airflow is supplied to the guide means and the manner in which the jetstreams are formed is not critical; however, the specific directions ofthe jets streams are. It is important that the proper angle andorientation of the jet streams be maintained so as to provide a net flowof air capable of sweeping an individual or object passing through saidsampling chamber means 100 while maintaining the integrity of the volumeof air within the sampling chamber means 100.

Referring now to FIG. 5, the volume of air 120 enclosed by the dashedlines indicates the total volume of air moving towards the collectionduct 110 and sampling port 118a shown in FIG. 2. The upward flow of airstarts at approximately one foot in from the perimeter of the chamberfloor 104. This figure indicates the net upward flow of air, and doesnot intend to exclude other air currents present in the chamber, becauseother currents are present; however, their direction is not upward. Ascan be seen in FIG. 5, the effect of the generated internal air flowsand the shape of the ceiling 106 shown in FIG. 2 tends to focus orconcentrate the large volume of air flowing upwards to a smaller, butmore concentrated volume of air. Arrows 122a-c, 124a-c and 126a-cindicate the velocities of the air mass at different stages in the flow.In the lower to middle regions, the air flow is 2-3 m/sec, and as theair mass approaches the low pressure region, the velocity increases to4-5 m/sec.

Turning to FIG. 6, a diagrammatic side view of the chamber 100 is shown.The region indicated by the dotted lines 128 and 130 indicate the regionin which cross-contamination of the internal air volume with the ambientenvironment occurs. As indicated by arrows 132a-c, air from thesurrounding environment enters the chamber 100 at approximately 0.5m/sec. The air from the outside environment is drawn in by theaerodynamics created by the internal air flow. This air flow into thechamber 100 results in one half of the internal air to be exchanged withthe outside air in approximately 30 seconds. Since the collection timetakes approximately one second, the cross-contamination is minimal. Theonly way to maintain absolute integrity of the internal air volume is toprovide rotating doors with a seal, and this however, would result inundesirable time delays.

SAMPLE COLLECTOR AND PRECONCENTRATOR

The sample collector and preconcentrator (SCAP) is used as part of theoverall system to enchance overall system sensitivity and selectivity.In general terms, the SCAP must simply discard, in a multi-step process,non-required molecules of air while not losing the targeted molecules ofinterest. In the sample collection and preconcentration step, thetargeted materials are adsorbed onto a selected substrate, and thenselectively desorbed. This process is repeated through a series of stepswhich decrease sample volume and increase sample concentration.

As illustrated in FIG. 7, the SCAP 200 is supplied with sample air bypipe 118 which extends to the sampling chamber 100. During samplingperiods a high suction fan 202 draws the sample volume through thesampling port 118a. The fan 202 is connected to pipe 118 on the suctionside with the discharge side connected to a vent or exhaust system tothe ambient environment.

The first stage of the concentration process involves the primarypreconcentrator 201 which consists essentially of a rotating filteringmeans 204. The air sample drawn from the sampling chamber 100 is drawnthrough filtering means 204. The filtering means 204 consists of twointerconnected filtering elements 206 and 208. The filtering elements206 and 208 are wire screens which hold an adsorbing material. Eachfiltering element 206 and 208 may be rotated through either of twopositions. Position 1 is in line with pipe 118 and position 2 is in linewith a secondary preconcentrator 203. The positions of the filteringelements 206 and 208 are changed by a control system which in thisembodiment is a hydraulic actuation system 210 which is connected tofiltering means 204 by shaft 212 which lifts movable platform 211 tomove each of the filter elements into a sealed connection at position 1and at position 2. A preconcentrator control unit 214 is also connectedto filtering means 204 by shaft 216. The hydraulic actuation system 210is comprised of a hydraulic control unit 210a and a hydraulic pump 210band is operable to lower and raise holding elements 205 and 207, intothe unlocked and locked positions respectively. When it is time torotate the filters 206 and 208, hydraulic actuation system 210 lowersholding elements 207 and 205 which engage filter elements 206 and 208respectively. Upon engagement of the filter elements 206 and 208,preconcentrator control unit 214, which is a computer controlled steppermotor, is operable to rotate filtering elements 206 and 208 betweenpositions 1 and 2 via shaft 216. The control of the hydraulic actuationsystem 210 and the preconcentrator control unit 214 is accomplished viathe control system which will be fully explained in subsequentparagraphs.

In a second embodiment the filtering means 204 consists of threeinterconnected filtering elements 206, 208 and 209 as shown in FIG. 8.Filter element 209 like filter elements 206 and 208 is a wire screenwhich holds the adsorbing material. Each filtering element 206, 208 and209 may be rotated through either of three positions. Position 1 is inline with pipe 118, position 2 is in line with a secondarypreconcentrator 203, and position 3 is exactly in between position 1 andposition 2. FIG. 9 shows a plane view of the three filter elements 206,208, and 209 spaced 20 degrees apart on movable platform 211. Thepositions of the filtering elements 206, 208 and 209 are changed by acontrol system which in this embodiment is a hydraulic actuation system210 which is connected to filtering means 204 by shaft 212 which liftsmovable platform 211 to move each of the filter elements into a sealedconnection at position 1, into a sealed connection at position 2 and atposition 3. The hydraulic actuation system 210 is comprised of ahydraulic control unit 210a and a hydraulic pump 210b and is operable tolower and raise holding elements 205, 207 and 215 into the unlocked andlocked positions respectively. When it is time to rotate the filters206, 208 and 209, hydraulic actuation system 210 lowers holding elements207, 205 and 215 which engage filter elements 206, 208 and 209,respectively. Upon engagement of the filter elements 206, 208 and 209,preconcentration control unit 214, which is a computer controlledstepper motor, is operable to rotate filtering elements 206, 208 and 209between positions 1, 2 and 3 via shaft 216.

Referring now to FIG. 7, the two filter process is described. During asampling period which is controlled by the control system, fan 202 drawsthe sample from the chamber 100 and through filter element 206 which isposition 1. Filter clement 206 collects the vapor and/or particulatematter contained in the air sample on an adsorption substrate. Thefilter element 206 comprises an adsorber that is selected to haveenhanced adsorption for the target materials and lessor adsorption forany contaminants. When the air sample passes through the filter element206 containing the adsorber, the adsorber preferentially selects asample of the target materials, and other contaminants arc passed on tobe vented or exhausted by fan 202. Upon completion of the samplingperiod, and adsorption of the target materials onto filter element 206,filter element 206 is switched to position 2 by the preconcentratorcontrol unit 214 and raised into a locked position by the hydraulicactuation system 210 so the desorption of the target materials canoccur.

In the desorption process, a stream of pure gas is passed over theadsorber containing the target materials and any remaining contaminants.The pure gas, which is usually an inert gas, is supplied from a gassupply 218 and transported to position 2 of filter means 204 by gas line220. This pure gas flow is much smaller then the volume of air used inthe sampling chamber 100. The temperature of the adsorber is raised in acontrolled fashion by the control system, illustrated in FIG. 13. Thetemperature of the filter being desorbed is raised by either a heatexchanger 213 or by the temperature of the pure gas from source 218. Ifthe temperature of the filter being desorbed is raised utilizing thepure gas, then the gas flow is diverted to a heating element (not shown)where it is raised to the proper temperature. When the desorptiontemperature for the target material is reached, the temperature is heldconstant and the pure gas flow is quickly switched to the desorptionstage in the concentration process. The heated gas then desorbs thetarget materials and carries them on to the next stage. The gas flowcontaining the target materials is routed to the secondarypreconcentrator 203 or interface unit via gas line 222. As thedesorption process is rapid, only a small volume of gas is transferredwhich results in the next stage receiving the target materials in aconcentrated form.

The primary concentration of the target materials is a continuous twostep process because of the two filter elements 206 and 208 both containadsorbing substrates. When filter element 206 is adsorbing the targetmaterials, filter element 208 is in the desorption process. Uponcompletion of the desorption of the target materials from element 208,the adsorbing material of element 208 is purified from materials andcontaminants and thus ready to be used as the adsorber in position 1.While a pair of rotating filter elements is illustrated in FIG. 7, itwould also be possible to use single use strip media which traversesfrom the absorbing station to the desorbing station, or to hold theposition of the filters fixed and alternate the sample and purge airstreams to absorb and desorb the target materials.

Referring to FIG. 8, the three filter process is now described. In asecond embodiment for the primary preconcentrator 201, a third filterelement 209 is added, thus making the primary concentration of thetarget materials a continuous three step process, because the threefilter elements 206, 208 and 209 all contain adsorbing substrates. Whenfilter element 206 is adsorbing the target materials, filter element 208is in the desorption process, and filter element 209 is be added toprovide for a thermal cleansing of any vapors or particulates which mayremain after the desorption process. When a particular filter element isin position 3, the pure gas supplied from gas supply means 218 is routedto position 3 of filter means 204 by gas line 220. The gas flow furthersweeps the particular filter element in an attempt to further purify theadsorbing material from contaminants. The exiting gas with contaminantsis exhausted to the ambient environment. A valve 217 is located in linewith gas line 220 and is operable to switch the gas flow from position 2to position 3 and vice versa.

The treatment of particulates and gaseous materials is slightlydifferent at the first step of the concentration process. Theparticulates may be small particles or droplets of the target materialitself or small particulates or droplets attached to dust particles orother vapor droplets. For particulates, the first stage is a filter orscreen having selective adsorption characteristics in the path of thesample air flow from the sampling chamber 100. The particulates arephysically trapped or adsorbed on this filter, and then the filter, or aportion of it, is physically transferred to a heated chamber and rapidlyheated to a temperature that is sufficient to vaporize withoutdecomposing the target particulates. A small quantity of heated purecarrier gas is admitted to the chamber to carry the now vaporizedmaterial to the next stage of the process. As stated previouslY, theheated gas can be used for supplying the heat for vaporization.

It is usually the case that the filter used in the sampling air flow forparticulate materials is also the absorber for gaseous materials andtherefore, as is shown in FIG. 7 a single primary preconcentrator 207can be used to capture both particulate materials and gaseous materials.It is necessary to sample target materials as particulates becausecertain target materials may have too low a vapor pressure at roomtemperature to be sampled as gas or vapor. In addition, it is possiblethat the target material itself has a tendency to be present in thesample volume as an adsorbate on particulate material independent ofvapor pressure considerations.

In the subsequent stages of concentration the selectable adsorbers arefixed and confined to metallic tubes. The sample and purge carrier gasflows are manipulated by switching valves which are under computercontrol. Referring once again to FIG. 7, the primary preconcentrator 201is connected to the interface 203 by gas flow line 222. The interface203, contains a secondary preconcentrator 224 and a multiport valvesystem 226. The purpose of the multi-port valve system 226 is forswitching between the gas supply line 230 which is supplied by gassupply 228, the preconcentrator 224 adsorption tubes, the gas flow line222 from the primary preconcentrator 201 and the gas flow line 232 tothe chemical analyzers 234 and 236. Basically, the multi-port valvesystem 226 is a switching network. The secondary preconcentrator 224 isa series of adsorption tubes. The multi-port valve system 226 is drivenby an interface control unit 238 which is simply a stepper motor torotate the valves in the multiport valve system 226 when commanded to doso by the computer. The interface 203 represents a generic block ofsecondary preconcentrators, and thus one can cascade a series ofmultiport valve systems and adsorption tubes in an attempt to furtherpurify the sample to be analyzed.

The adsorber tubes are very rapidly heated to and held at the selectedpredetermined temperature by heating the surrounding metallic tube orthe adsorber tube directly. This is usually done by passing a controlledelectrical current through the tube and using the tube itself as theheating element. In the case of larger adsorbent containing tubes, forthe heating times of tens, to a very few hundreds of milliseconds, thiscurrent may be several hundred amperes. The temperature may be measuredby brazing a tiny, very low mass thermocouple or thermistor to the tube.The thermocouple must be small enough so as not to affect the tube inany manner and it must be capable of responding rapidly. Thethermocouple feeds the measured temperature to the computer of thecontrol system wherein the computer controls the amount of currentflowing through the tubes. Basically, the computer forms the digitalclosure of an analog control loop. The computer is used to monitor andcontrol the temperature because the proper thermal program for thedesired target materials or material is critical. The size of the tubesis decreased in steps to reflect the decrease in volume of gascontaining the samples and may eventually reach the internal size of acapillary gas chromatograph column.

The multiport valve system 226 is a switching network with multipleports as the name suggests. In one embodiment of the present invention,the multiport valve system 226 is a six-port valve. FIGS. 10A and 10Brepresent the two positions that the six-port valve 226 can occupy. Theinterface control unit 238, is a stepper motor, and is operable toswitch the six-port valve 226 between the two positions. In eitherposition, only pairs of ports are connected. In position 1, illustratedin FIG. 10B, ports 1 and 2, 3 and 4, and 5 and 6 are connected, and inposition 2, illustrated in FIG. 10A, ports 2 and 3, 4 and 5, and 6 and 1are connected. Position 2 places the adsorb-desorb tube 248 in the loadposition. The gas flow line 222 shown in FIG. 7 carries the gascontaining the target material and some contaminants into port 1indicated at 242 in FIG. 10A of valve 226 wherein the gas automaticallyflows through an internal passageway 244 to port 6, indicated at 246 inFIG. 10A. Connected between port 6 and port 3 is an externaladsorption/desorption tube 248 in which the gas containing the targetmaterial and some minor contaminants pass through. The adsorbingmaterial inside the tube 248 is specifically targeted for the targetmaterial; therefore, the carrier gas and the contaminants flow throughthe tube 248 to port 3, indicated at 250 while the target material isadsorbed within the tube. The carrier gas and contaminants flow fromport 3 indicated at 250 in FIG. 10A to port 2 indicated at 252 in FIG.10A through internal passageway 254, and is vented to the externalatmosphere through exhaust line 256. Pure carrier gas supplied from gassupply 228 shown in FIG. 7 is fed into port 4 indicated at 258 via line230. The pure carrier gas automatically flows from port 4 indicated at258 to port 5 indicated at 260 via internal passageway 262. The carriergas then flows from port 5, indicated at 260 to either of the chemicalanalyzers 234 or 236 via line 264. The analyzers 234, 236 require acontinuous gas flow to remain operational. The use of multiport valvesystems allows pure carrier to be fed gas continuously to the analyzers234, 236, even when the adsorb/desorb tube 248 is in the adsorb cycle.

At the end of the adsorption cycle, the computer of the control systemthen automatically switches the six-port valve 226 into position 1 whichis the desorb mode as shown in FIG. 10B. Port 1, indicated at 242 inFIG. 10B still receives gas from the primary concentrator 201 via line230; however, the gas flows from port 1, indicated at 242 to port 2,indicated at 252 via internal passageway 268 and is vented to theatmosphere via exhaust line 256. Port 4, indicated at 258 is injectedwith pure carrier gas from supply 228 via line 230 which flows to port3, indicated at 250 via internal passageway 270. As stated before, port3, indicated at 250 and port 6, indicated at 246 are connected via anexternal adsorption/desorption tube 248; however, in this position, thecarrier gas is flowing through the tube 248 in the opposite direction.Therefore, when the tube 248 is heated to desorption temperature, thegas will sweep the desorbed target material and carry it to port 6,indicated at 246 free of atmospheric contaminants. From port 6,indicated at 246, the target material flows to port 5, indicated at 260,via internal passageway 272 and to the chemical analyzers 234 and 236via line 264.

The external adsorption/desorption tube 248 is electrically insulatedfrom the valve body and contains a selected quantity of the adsorbingmaterial which has the best characteristics for adsorbing the targetmaterial. High current connections are made to the ends of this tube 248and are shown in FIGS. 10A and 10B as electric lines 280 and 282. Lines280 and 282 are connected on the other end to a controlled currentsource 281. A thermocouple 283 is shown attached to tube 248 in FIGS.10A and 10B. This thermocouple 283 as stated previously, is used toraise the temperature of the tube 248 so as to achieve the propertemperatures for desorption. The gas sample which contains the targetmaterial, contaminants and excess gas, passes through the tube 248 andbecause it is cold, and the adsorber material has been selected to be astrong adsorber for the target- material, most of the sample will beadsorbed at the end of the tube 248 near port 6. The contaminants areless strongly adsorbed and thus any adsorption of them will bethroughout the length of the tube 248. Also, because the contaminantsare not strongly adsorbed a larger portion of them will pass through thetube to the exhaust vent 256 and be discarded.

A desirable property of thermal desorption of gases or vapors on solidor liquid substrates is that the process can be highly thermallysensitive and thermally dependent. At a specified temperature the amountof any material desorbed is related to its physical and chemicalproperties and the physical and chemical properties of the adsorbingmaterial. It is possible to choose adsorbing materials such that thecontaminating materials are desorbed at a workable lower temperaturethan the target materials.

Careful thermal programming allows one to use these properties. Anexample is to heat the desorber tube 248 in a controlled fashion withthe valve 226 in position 2. The contaminants such as water vapor etc.are not stronglY adsorbed and a low temperature will cause a majorportion of them to leave the adsorber and pass out of the system throughthe vent. At the same time, the target materials will not be desorbedand will remain at the end of the adsorber tube 248 adjacent port 6. Ifthe position of the rotor in the six-port valve is now changed to the 1position, two important changes are made. The adsorber tube is nowconnected to the next stage in the sequence and the pure carrier gasflows through the adsorber tube in the opposite direction to theprevious gas flow direction. A rapid controlled increase in temperaturewill now cause the sample to be desorbed in a short period of time. Thisresults in a sample which has been purified by the previously describedadsorption and desorption process passing to the next stage in theprocess, contained in the minimum of pure carrier gas. Thus the samplehas been twice purified of contaminants and concentrated in a muchreduced volume of pure inert carrier gas.

The next step in the purification and concentration process may beanother six-port valve with a smaller diameter desorption tube. Thefinal desorption tube should match in diameter the size of the column inone of the analyzers, such as analyzers 234, which is a gaschromatograph. If this is done, it results in ideal sample injectioninto the gas chromatograph. In fact, it is possible by careful designand construction to have the desorber tube the same internal diameter asa capillary gas chromatograph column. It is possible to use the tubeconnecting two six-port valves as a desorber tube for purification andconcentration purposes. It may be packed with adsorber and fitted withheating and temperature measuring equipment such as electricalconnections and thermocouples.

The adsorbent material used in the various stages of concentration ofthe target materials may be selected from a group of materials commonlyused for vapor sampling including Tenax and Carbotrap. There are otheradsorbing materials that can be used with the present inventiondepending on the particular materials that are to be detected andisolated.

The SCAP 200 also contains an attachment for a portable sampling device292 which is shown in FIG. 11A. The connection is a pipe 223 which isconnected to pipe 118 shown in FIG. 7 or 8 through valve 221. The pipe118 may be stainless steel, aluminum or even ABS plastic. Normally, fan202 draws an air sample from the chamber 100; however, when valve 299closes off the chamber 100 and valve 221 is opened, fan 202 will draw anair sample from the wand 292. The wand 292 is capable of drawing vaporand/or particulate emissions from a specific area on an individual orobject. The wand 292 is used to sample an individual intensively whenthe results from the pass through the chamber 100 are inconclusive.

A second use for the hand held wand 292 would be to draw vapor and/orparticulate emissions from baggage that is going to be stored in thecargo hold of the airplane. The system including the hand held wand 292has proven very effective as a means of detecting explosive vapors inpackages and baggage. In tests wherein the hand held wand 292 has beenheld against cardboard box packages and various types of luggage,positive identification of low levels of explosive vapors, equivalent toapproximately a third of a stick of dynamite, are made. In addition, thehand held wand 292 can be attached to a sampling box 294 as shown inFIG. 11B that is placed over luggage to enhance the efficiency ofdetection and provides a means to automate baggage screening byincluding a conveyor belt 298. The wand 292 is attached to sampling box294 through connection means 296.

In a second embodiment for the portable sampling device 292, aparticulate collector and detector (PCAD) 400 is incorporated. The PCAD400 is located in line with stainless steel pipe 223 between valve 221and flexible hose 290 as shown in FIG. 12a. The PCAD 400 consists of arotating circular plane 402, a collection chamber 404, a desorptionchamber 406, a flushing chamber 408, a stepper motor 410, a six-portvalve 412, a pair of gas supplies 414a and 414b and a chemical analyzer416. The rotating circular plane 402 has three circular holes 418, 420,and 422 equally spaced 120 degrees apart and covered with stainlesssteel mesh screens 424, 426 and 428. The rotating circular plane 402,which is actuated by the stepper motor 410, is rotated 120 degrees everysampling period so that each one of the holes 418, 420 and 422 occupieseither the collection chamber 404, the desorption chamber 406 or theflushing chamber 408. To illustrate the operation of the PCAD 400, acomplete 360 degree rotation of the circular plane 402 will bedescribed.

For the purposes of this illustration, it is assumed that hole 418 withscreen 424 is inside the collection chamber 404 at the start-up time. Inthis position, the hole 418 and screen 424 is directly in line withstainless steel pipe 223, and thus the screen 424 covering hole 418 iscapable of collecting particulate matter that may be drawn from the handheld wand 292 during a sampling period. The particulate matter may besmall particles or droplets of the target material itself or smallparticulates or droplets attached to dust particles or other vapordroplets. The particulate matter drawn in through wand 292 is physicallytrapped or adsorbed on screen 424. Any particulate matter not trapped onthe screen 424 passes directly through to the SCAP 200 for standardpreconcentration. The stainless steel screen can be varied in mesh sizeso as to be able to collect specific size particulates. Upon completionof the sampling period, stepper motor 410 is engaged by the controlsystem (described subsequently) and rotates circular plane 120 degreesplacing hole 418 and screen 424 inside the desorption chamber 406.

The desorption chamber 406 is a sealed chamber which contains a pair ofelectrical terminals 430 which connect to stainless steel screen 424when that particular screen occupies the desorption chamber 406. Thepair of terminals 430 provide a computer controlled current to thestainless steel screen 424 in order to generate a specific amount ofheat energy to effectively desorb the collected particulate matter.After the desired temperature for desorption is reached, a smallquantity of carrier gas from gas supply means 414a sweeps the desorbedmaterial from the desorption chamber 406 via line 401 into the six-portvalve 412. The operation of the six-port valve 412 is exactly the sameas was described previously with an injection position and a loadposition. During the injection cycle, the further concentrated sample isinjected into the chemical analyzer 416. In this embodiment, theanalyzer 416 is a gas chromatograph. Note that during the desorptionprocess wherein hole 418 and screen 424 are in the desorption chamber406, hole 420 and screen 426 are inside the collection chamber 404collecting the next sample of particulate matter. Upon completion of thedesorption of the particulate matter, the stepper motor 410 is engagedand circular plane 402 is rotated 120 degrees placing hole 418 andscreen 424 inside the flushing chamber 408, hole 420 and screen 426inside the desorption chamber 406 and hole 422 and screen 428 in thecollection chamber 404.

The flushing chamber 408 is a sealed chamber similar to desorptionchamber 406. In this position, a second pair of electrical terminals 432are connected to screen 424. The second pair of electrical terminals 432provide a computer controlled current to generate a specific amount ofheat energy to desorb any remaining particulate matter remaining onscreen 424. A gas flow from gas supply 414a is used to sweep thedesorbed material into the ambient environment through a vent in thechamber 408. Note that during the flushing process, hole 420 and screen426 are inside the desorption chamber 406, and hole 422 and screen 428are in the collection chamber 404 collecting the next sample ofparticulate matter.

In an alternate embodiment for the PCAD 400, the analyzer 416 is a ionmobility spectrometer. The alternate embodiment is shown in FIG. 12b. Asis shown in the figure, the only significant change is the substitutionof a three-way valve 434 for the six-port valve 412. In this embodiment,the desorption process is identical to that previously described;however, the carrier gas sweeps the desorbed material into a three-wayvalve 434 instead of the six-port valve 412. The three-way valve 434 isa simple device which either vents the incoming flow of gas from gassupply 414a into the ambient environment or into the analyzer 416.

The PCAD 400 is designed in such a way that the movement of the circularplane 402 places holes 418, 420 and 422 in tightly sealed positions ateach location so there is no contamination with the ambient air. Theprecise movement of the circular plane 402 is automatically controlledby the control system (to be described subsequently) and actuated by thestepper motor 410.

ANALYSIS

The analysis of the purified target material consists of identifying thematerials and determining the amounts present. Because the originalconcentrations were so low with respect to many other common ambientmaterials it is possible for there to be, even under the best ofpurification and concentration systems, some remaining impurities ofmaterials with similar characteristics to the target materials. Thus theanalysis system must be capable of separating the target materialresponse from the response due to interfering materials.

Two forms of analysis systems are used either separately or incombination. These systems are an ion mobility spectrometer (IMS) 236based analysis system and a gas chromatograph (GC) 234 based system. Thefinal detector for the GC 234 is usually an electron capture detector(ECD) but the IMS 236 can also be used as the detector if desired.Depending on the application, a photo ionization detector or anitrogen-phosphorus detector or some other detector may be also usedfollowing this. The GC 234 may be of the "packed column" type or thecapillary column type. Both analyzers 234 and 236 can be used separatelyor in a combined fashion Valve 235 is used to direct the collected andpurified sample to either or both of the analyzers. The analyzer 416used in the PCAD 400 is either a gas chromatograph or ion mobilityspectrometer and it exists as a separate entity from the analyzers ofthe SCAP 200, but its operation is identical to the above describedanalyzers.

Whatever analysis system is used the analysis must be completed in atime that is short enough that the free flow of people, luggage andbaggage is not unduly inhibited. This also implies that the time for theconcentration and purification process is short as well.

If all the valves in the system are motor driven or solenoid drivenvalves, the flow directions timings and magnitude may be controlled andvaried. The time and temperature parameters are controlled and variable.Thus the physical characteristics of the complete system may be adjustedto detect a wide range of target materials and the sensitivities may beadjusted to accommodate a wide range of threats as perceived by theauthorities using the system.

All the processes involved in the collection and concentration as wellas the final analysis of the collected material is controlled by thecomputer of the control and data processing system and will by fullyexplained in the following section.

CONTROL AND DATA PROCESSING

The primary requirement for the control and data processing system ofthe screening system is that it reports the presence of, and ifrequired, the level of specified substances. This means that theequipment must be configured and controlled to make the requiredmeasurement and it also means that the result must be presented to theuser in a usable form. The subject or target materials may be present invarying amounts in the environment of the system and therefore, thesystem must be capable of distinguishing between this background leveland an alarm level. It may also be a requirement to report on thisbackground level.

A secondary requirement for the control and data processing system ofthe integrated system is self diagnostic, as there may be considerabletime between alarms, the control and data processing system must becapable of performing confidence checks that are satisfactory to theoperator on demand. There must also be routine self checks andcalibration procedures performed on the total system by the control anddata processing system. Basically, this ensures that the test results,whether positive or negative, must be believable.

A third requirement for the control and data processing system is easeof reconfiguration and versatility. The range of target materials may bechanged from time to time, and the system must be capable of varying itsinternal operation parameters under program control to detect thesematerials. It is desirable that the rigor of the measurement in terms oftime constraints and number and types of substances detected bealterable in an expeditious fashion at any time. The user's requirementsin terms of level of threat and types of materials may quickly changeand the equipment must respond to these changing needs.

The final requirement for the control and data processing system is thatthe parameters and operations of the sampling chamber and the SCAP mustbe monitored and controlled. This means that all internal timings,temperatures and mechanical components must be controllable by thecontrol and data processing system.

The primary method of achieving these requirements is to put the totalsystem under the control of a stored program digital computer. Thiscomputer through a series of modularized software routines performs thedata analysis and presents the results in the required form to the user.The computer through another series of modularized software routinescontinuously performs self diagnostic and self calibration procedures onthe total system, and alerts the user to any potential problems. Thecomputer through still another set of modularized software routinescontrols all the processes of the total system and shall be more fullyexplained in subsequent paragraphs.

One primary benefit of this system of control is reliability. Bythemselves the components are rugged and reliable and not prone tofailure. However, any system made up of many items is subject to driftsdue to ambient changes and time. By having all components under programcontrol and by arranging for a known input to the system such as acontrolled injection of target material or target simulant, there can bea calibration and self-diagnostic program. The function of this programis to calibrate the entire system and determine and store the requiredtime, and temperature parameters etc. If these parameters are not withinspecified limits for any reason, the program can alert the user. Guidedby a service program the user response can range from immediate shutdownto scheduling service at a later date, to simply noting thecircumstances. By use of a modem this information can be easilytransmitted to anywhere in the world. The other aspect of reliability ina system of this type is that the user must know that the system isreliable. Hopefully there will be very long periods of time betweenactual alarm events. However, if there is a calibration and selfdiagnostic program and associated hardware for realistic sampleinjection, the user can generate, at anytime, an actual/simulated alarmevent as a confidence check.

The second primary benefit of this system of control is versatility. Itis advantageous for the system to have the capability of detecting awide range of explosives, a range of controlled chemical agents, drugs,and narcotics etc. All these materials have differing physical andchemical properties. These properties give rise to a set of internalparameters for optimum detection. However these parameters will be lessthan optimum for some other materials. But, if these parameters are allcontrollable and easily changed such as by simply reading in oractivating a different program in the computer memory, then the user caneffectively change the system to meet what is considered to be thethreat at that time without making any hardware changes.

Referring now to FIG. 13, there is shown a block diagram representationof the control and data processing system 300 and its associatedperipheral elements. The digital computer 302 or processor is an AT typepersonal computer running at 10 MHz and has a standard video displayterminal 304. The computer 302 is responsible for process control, dataacquisition, data analysis and display of results. In addition, asmentioned previously, the computer 302 also contains software routinesfor self diagnostic and self calibration procedures. The computer 302receives power from the power distribution unit 306 as does the samplingchamber 100, the hydraulic pump 210b which supplies hydraulic pressurefor the hydraulic control unit 210a, and the process control unit 308.The process and control unit 308 under the control of the computer 302interfaces and provides the necessary signals to run the hydrauliccontrol unit 210a,the preconcentrator control unit 214 and the interfacecontrol unit 238.

The process and control unit 308 is a standard interface unit betweencomputer 302 and the various actuators. The hydraulic actuator unit 210adetermines the drive direction of the hydraulic piston which travels upand down to unlock and lock the filter elements 206 and 208 of theprimary preconcentrator 201, as shown in FIG. 7, so they can be rotatedfrom position 1 to position 2 as described in the previous section.Under software control, the process control unit 308 outputs commands tothe hydraulic actuator unit 210a which is a two-way solenoid, not shown,and engages or disengages the hydraulic piston. The preconcentratoractuator unit 214 is a stepper motor which rotates the filter elements206 and 208 after they are no longer locked in place by the hydraulicactuator unit 210a. The stepper motor is run under software control. Theinterface actuator unit 238 is also a stepper motor, and it is used torotate the multi-port valve 226, used in the secondary preconcentrator203, from position 1 to position 2 and vice versa. The PCAD actuatorunit comprises two stepper motors, one for the rotation of the circularplane 402, and one for the actuation of the six-port valve 412 or thethree-way valve 434. Data from the analyzers 234 and 236 is broughtdirectly into the computer 302 for processing. Data from the gaschromatograph/ECD system 234 is taken into the computer 302 as a varyingfrequency, and data from the IMS system 236 is taken into the computer302 as a varying analog voltage. The data input to the computer 302 iscorrelated by processor 302 to the process control module 308 whichgenerates the necessary interrupts for processor 302 so the data can beinput at the proper time intervals.

The computer 302 has an internal clock which provides the referenceclock for all timing sequences. Therefore, because all the valves andmechanical motions are being actuated by the computer, all gas andsample flows in the equipment are controllable with respect to the timeof actuation. The relative sequencing and timing of actuations aresimply steps in a stored program in the memory of the computer. Inaddition, all the temperatures in the equipment are read into thecomputer and all heating functions are actuated by the computer.Therefore, all the temperatures and their magnitudes at any time andrate of change with respect to time are under program control. The dataoutput from the ECD 234 and the IMS 236 are processed as necessary andthe required information is extracted and displayed by the samecomputer.

FIG. 14a is a flow chart 500 showing the overall process control asaccomplished by the control and data processing systems and run by thecomputer 302. Block 502 of flow chart 500 is simply the starting pointor entry into the entire software package. The Run Diagnostics block 504represents the block of software that is responsible for self diagnosticand self calibration. The Sample Air block 506 represents the block ofcode that causes the air sample drawn from the sampling port of thesampling chamber to be drawn into the SCAP. After the Sample Air Block506, the flow chart 500 diverges into two paths that can runsimultaneously. One path represents normal SCAP 200 operation while thesecond path represents PCAD 400 operation. The first path is as follows:The Release Filters block 508 represents the block of software that isresponsible for the control of the hydraulic control unit. The RotateFilters block 510 represents the block of software responsible for thecontrol of the preconcentrator control unit. The Lock Filters block 512represents the block of software that is responsible for the control ofthe hydraulic control unit in that it commands the unit to lock thefilter elements in the holding means. The Desorb Vapor block 514represents the block of software that is responsible for the controllingof the heating means and the low of pure gas in the desorption process.The Rotate Multiport Valve block 516 represents the block of softwarethat is responsible for controlling the multiport valve of the secondarypreconcentrator so that the concentrated sample is properlY routed tothe analyzers. The Acquire Data block 518 represents the block ofsoftware that is responsible for the acquisition of data from theanalyzers and the subsequent analysis and display of the resultant data.The software is a cyclic process and following step 518, returns tosampling step 506 and continues until stopped. The second path is asfollows: The PCAD Rotate Filters block 520 represents the block ofsoftware responsible for the control of the rotation of the circularplane. The PCAD Heat Collected Particulate Matter block 522 representsthe block of software responsible for the electrical heating of thestainless steel screens during the desorption process. The PCAD RotateSix-Port Valve block 524 represents the block of software responsiblefor controlling the six-port valve so that the concentrated sample isproperly routed to the analyzer. The PCAD Acquire Data block 526represents the block of software that is responsible for the acquisitionof data from the analyzers and the subsequent analysis and display ofthe resultant data. The software is a cyclic process and following thestep of block 526, returns to sampling step 506 and continues untilstopped. As stated previously, the software routine is modularized andtherefore can be easily changed, updated, removed or added on to.

FIG. 14b is a flow chart 500' which shows an identical process as doesthe flow chart 500 in FIG. 14a with one exception. In flow chart 500',the PCAD Rotate Six-Port valve block 524 of FIG. 14a is replaced by aPCAD Actuate Three-Way Valve block 528. The PCAD Actuate Three-Way Valveblock 528 represents the block of software responsible for controllingthe three-way valve in the ion mobility embodiment so that theconcentrated sample is properly routed to the analyzer.

There are two schemes that exist for the screening process. Thesequential scheme requires approximately 14.0 seconds to complete onescreening cycle and the concurrent scheme requires approximately 3.6seconds to complete one screening cycle. Both schemes are implementedusing flow charts 500 and 500' illustrated in FIGS. 14a and 14b;however, as the name implies, the concurrent scheme involves performingcertain of the operations involved in the screening process in anoverlapping or multi-tasking environment. Basically, in the concurrentscheme, the software routines are run in a foreground/backgroundscenario in a true interrupt mode. In this type of scenario themechanical operations can be run in background while the analysis anddata processing can be run in foreground. FIGS. 14a and 14b are ageneral representation of the software and should not be construed as atiming diagram. Table 1 given below illustrates the required steps andassociated times involved in the screening procedure utilizing thesequential scheme.

                  TABLE 1                                                         ______________________________________                                        SAMPLE COLLECTION         5.0 seconds                                         PRIMARY CONCENTRATION STAGE                                                                             3.0 seconds                                         SECONDARY CONCENTRATION STAGE                                                                           2.0 seconds                                         ANALYSIS                  3.0 seconds                                         DATA PROCESSING/REPORTING 1.0 seconds                                         TOTAL SCREENING TIME      14.0 seconds                                        ______________________________________                                    

Referring now to FIG. 15, a sequence diagram 600 or timing chart isgiven in order to illustrate the various time parameters for each givenin the concurrent sampling scheme. Each time bar is comprised of fiveboxes indicating the various steps in the process. Box 602 representsthe air sampling step time, box 604 represents the time for themechanical steps involved in the collection of the sample, box 606represents the time associated for injecting the concentrated sampleinto the chemical analyzers, and box 610 represents the analysis time.Since it takes approximately 2.5 seconds to pass through the portal, twopeople can pass through in 5.0 seconds, and thus the timing chart 600 isshown for two people. To calculate the total time for a single person,which is approximately 3.6 seconds, the total time for the first twopeople to be screened, which is 14.4 seconds, has subtracted from it thetime for sampling and collecting the sample from the next two people,which is approximately 7.2 seconds, resulting in a time of approximately7.2 seconds for two people and 3.6 seconds for a single person. Asindicated in chart 600, the concurrent scheme overlaps in the samplingand collection periods. The three remaining time lines are identicalnumerals with prime, double prime and triple prime added.

Although shown and described in what is believed to be the mostpractical and preferred embodiments, it is apparent that departures fromspecific methods and designs described and shown will suggest themselvesto those skilled in the art and may be used without departing from thespirit and scope of the invention. The present invention is notrestricted to the particular constructions described and illustrated,but should be constructed to cohere of all modifications that may fallwithin the scope of the appended claims.

What is claimed:
 1. A portable explosive detection screening system forthe detection of concealed explosives, chemical agents and othercontrolled substances such as drugs or narcotics by detecting theirvapor or particulate emissions, said system comprising:(a) a portablesampling means for gathering a sample volume of air from a specific areaon a person or object to collect any vapor or particulate emissionstherefrom; (b) a sample collection means to collect vapor or particulateemissions in said sample volume of air, said sample collection meansincluding a particulate collection means for collecting and vaporizingparticulate emissions collected by said portable sampling means; (c)means for concentrating said vapor or vapor subsequently emitted by saidparticulate emissions, said means for concentrating having a first meansfor adsorption and a second means for desorption of said concentratedvapor; (d) a detecting means including a first detector responsive tosaid vapor desorbed from said second means for desorption to generate afirst signal and an alarm.
 2. The portable explosive detection screeningsystem of claim 1, wherein said sample collection means further includesa conduit for collecting said volume of air from said portable samplingmeans and transporting said volume of air to said particulate collectionmeans, and connecting said particulate collection means to said meansfor concentrating.
 3. The portable explosive detection screening systemof claim 2, wherein said portable sampling means includes a hand heldwand which is connected to said conduit and a suction fan for drawingsaid volume of air from said portable sampling means at predeterminedtimes, said hand held wand being connected to said conduit by a flexiblepipe.
 4. The portable explosive detection screening system of claim 3,wherein said particulate collection means comprises:a rotating plate,said rotating plate defining an axis of rotation and having at least twoopenings, said two openings being circumferentially spaced about saidaxis of rotation and supporting stainless steel mesh screens forcollecting particulate emissions from said portable sampling means; acollection chamber in line with said conduit means adjacent saidrotating plate, said stainless steel mesh screens being exposed to andadsorbing vapors and particulate emissions collected by said portablesampling means; and a desorption chamber adjacent said rotating plate,wherein said stainless steel mesh screens are heated to vaporize saidcollected emissions and desorb collected vapors.
 5. The portableexplosive detection screening system of claim 4, wherein saidparticulate collector further comprises an actuator means for rotatingsaid rotating plate a predetermined distance at predetermined times todefine a sampling period.
 6. The portable explosive detection screeningsystem of claim 5, wherein said desorption chamber comprises a firstpair of electrodes which connect to said stainless steel mesh screensand apply a current to said screen to rapidly heat said screens anddesorb the collected vapor and vaporize the collected particulateemissions.
 7. The portable explosive detection screening system of claim6, wherein said first detector further comprises a chemical analyzermeans.
 8. The portable explosive detection screening system of claim 7,which further includes a six-port valve, said six-port valve beingconnected between said desorption chamber and said chemical analyzermeans.
 9. The portable explosive detection screening system of claim 7which further includes a three-way valve means connected between saiddesorption chamber and said chemical analyzer.
 10. The portableexplosive detection screening system of claim 7 wherein said firstdetector includes an ion mobility spectrometer.
 11. The portableexplosive detection screening system of claim 5 wherein said actuatormeans comprises a stepper motor.
 12. The portable explosive detectionscreening system of claim 3 wherein said particulate collector meanscomprises:a rotating plate, said rotating plate defining an axis ofrotation and having three openings, said three openings beingcircumferentially spaced about said axis of rotation and supportingstainless steel mesh screens for collecting particulate emissions fromsaid portable sampling device; a collection chamber in line with saidconduit means adjacent said rotating plate, said stainless steel meshscreens being positioned to receive vapors and particulate emissionscollected by said portable sampling device; a desorption chamberadjacent said rotating plate, wherein said stainless steel mesh screensare heated to desorb said collected vapors and particulate emissions;and a flushing chamber adjacent said rotating plate, wherein saidstainless steel mesh screens are again heated to desorb any remainingvapors or collected particulate emissions, with said remaining desorbedvapors or particulate emissions vented to the ambient environment. 13.The portable explosive detection screening system of claim 12 whereinsaid particulate collector and detector means further comprises acontrol means for generating a plurality of sampling periods and anactuator means for rotating said rotating place a predetermined distanceduring each sampling period.
 14. The portable explosive detectionscreening system of claim 13 wherein said desorption chamber furtherincludes a first pair of electrodes which connect to said stainlesssteel mesh screens and apply a current to said screens to rapidly heatsaid screen and desorb the collected vapors and vaporized the collectedparticulate emissions.
 15. The portable explosive detection screeningsystem of claim 12 wherein said flushing chamber further includes asecond pair of electrodes which connect to said stainless steel meshscreens and supply a current to said screen to rapidly heat said screenand further desorb any remaining vapors or collected particulateemissions.
 16. The portable explosive detection screening system ofclaim 3 wherein said means for concentrating further includes a primarypreconcentrator.
 17. The portable explosive detection screening systemof claim 16 wherein said first means for adsorption and said secondmeans for desorption include a plurality of filter means mounted on amovable platform, which move from said adsorption chamber to saiddesorption chamber.
 18. The portable explosive detection screeningsystem of claim 17 wherein said plurality of filter means are movablebetween an adsorption position and a desorption position, each of saidfilter means being in line with said suction fan to adsorb vapor and/orparticulate emissions contained in said volume of air in said adsorptionposition, and each of said filter means being in line with secondarypreconcentrator when said adsorbed vapor and/or particulate emissionsare desorbed.
 19. The portable explosive detection screening system ofclaim 18 wherein said primary preconcentrator further comprises a seriesof three filters mounted on said movable platform.
 20. The portableexplosive detection screening system of claim 19 wherein said series ofthree filter means are movable between said adsorption position, saiddesorption position, and thermal cleaning position, each of said filtermeans being sequentially in line with said suction fan to adsorb vaporand/or particulate emissions contained in said volume of air in saidadsorption position, each of said filter means being sequentially inline with a secondary preconcentrator means when said adsorbed vaporand/or particulate emissions are desorbed, and each of said filter meansbeing sequentially in line with a thermal cleaning means when the otherfilters, are being adsorbed and desorbed.
 21. The portable explosivedetection screening system of claim 20 wherein said primarypreconcentrator comprises a gas supply means for supplying a clean gasflow to said series of filter means when said respective filter means isin said desorption position, wherein said clean gas flow is used todesorb and sweep said concentrated vapor and/or vapor emanating fromparticulate matter into said secondary preconcentrator means when saidfilter means is in said desorption position, and said clean gas flow isused to thermally clean and sweep residue into the ambient environmentwhen said respective filter is in said thermal cleaning position. 22.The portable explosive detection screening system of claim 21 whereinsaid clean gas in an inert gas.
 23. The portable explosive detectionscreening system of claim 22 wherein said series of filter meanscomprise wire screens which hold a selected adsorbing material coatedthereon.
 24. The portable explosive detection screening system of claim23 wherein said selected adsorbing material selectively absorbsexplosive compound vapors or explosive compound particulates.
 25. Theportable explosive detection screening system of claim 23 wherein saidselected adsorbing material selectively adsorbs narcotic compound vaporsor particulates.
 26. The portable explosive detection screening systemof claim 23 wherein said primary preconcentrator further comprises aheat exchanger for supplying heat to each of said filter means when theyare in said desorption and said thermal cleaning position to aid indesorbing the vapor and/or particulate emissions.
 27. The portableexplosive detection screening system of claim 1, wherein said detectingmeans includes a gas chromatograph.
 28. The portable explosive detectionscreening system for the detection of concealed explosives, chemicalagents and other controlled substances such as drugs or narcotics bydetecting their vapor or particular emissions, said systemcomprising:(a) a portable sampling means for gathering a sample volumeof air from a specific area on a person or object to collect any vaporor particulate emissions therefrom, said sampling means connected tosaid system by means of a flexible conduit, with said sample volume ofair drawn by a suction fan; (b) a primary preconcentratory means toselectively absorb vapor or particulate emissions in said sample volumeof air, said primary preconcentrator including first, second and thirdfiltering means with each filter means sequentially movable between anadsorption position, a desorption position, and a thermal cleaningposition, said second filter means being in said desorption positionwhen said first filter means is in said adsorption position and whensaid third filter means is in said thermal cleaning position, saiddesorption position having means to heat said filter to desorb saidvapor and to vaporize said collected particulate emissions; (c) adetecting means having at least a first detector responsive to vapordesorbed from said secondary preconcentrator to generate a first signaland an alarm.
 29. The portable explosive detection screening system ofclaim 28 wherein said first, second and third filter means are mountedon a rotatable platform and moved by a control system.
 30. The portableexplosive detection screening system of claim 29 wherein said controlsystem comprises:a hydraulic control unit and pump connected to saidrotatable platform by a rigid shaft, said hydraulic control unitoperable to move said platform from a locked position to an unlockedposition; and a preconcentrator control unit which is operable to rotatesaid platform when said platform is in the unlocked position.
 31. Theportable explosive detection system of claim 30 wherein saidpreconcentrator control unit is a stepper motor.
 32. The portableexplosive detection screening system of claim 28 wherein said systemfurther includes secondary preconcentrator which includes a multi-portvalve system.
 33. The portable explosive detection screening system ofclaim 32 wherein said multi-port valve system is a six-port valve whichincludes an adsorption/desorption tube selectively and sequentiallyconnected across two of said six-ports, said six-port valve beingrotatable between an adsorb position and an desorb position.
 34. Theportable explosive detection system of claim 33 wherein said six-portvalve is rotated by an electronic interface control unit.
 35. Theportable explosive detection system of claim 34 wherein said interfacecontrol unit includes a stepper motor.
 36. The portable explosivedetection screening system of claim 33 wherein said six-port valve is insaid adsorb position when said vapor and vapor emanating fromparticulate matter in the primary preconcentrator is passed through saidadsorption tube for further concentration.
 37. The portable explosivedetection screening system of claim 33 wherein said six-port valve is insaid desorb position when said concentrated vapor is desorbed and sweptinto said detecting means.
 38. The portable explosive detectionscreening system of claim 33 wherein said adsorption/desorption tube iselectrically connected to a controlled current source which is used toheat the tube to a predetermined temperature as part of the desorptionprocess.
 39. The portable explosive detection screening system of claim38 wherein said secondary preconcentrator means further comprises a gassupply means for sweeping said further concentrated vapor into saiddetection means.
 40. The portable explosive detection screening systemof claim 39 wherein said detecting means includes an ion mobilityspectrometer (IMS) for analyzing said further concentrated vapor andgenerating said first signal if a target material is detected.
 41. Theportable explosive detection screening system of claim 39 wherein saiddetecting means includes a gas chromatograph/electron capture detectorfor analyzing said further concentrated vapor and generating said firstsignal if a target material is detected.
 42. The portable explosivedetection screening system of claim 39 wherein said detecting meansincludes a photo ionization detector.
 43. The portable explosivedetection screening system of claim 39 wherein said detecting meansincludes a nitrogen phosphorous detectors.
 44. The portable explosivedetection screening system of claim 41 wherein said detecting meanscomprises an ion mobility spectrometer and a gas chromatograph/electroncapture detector for analyzing said further concentrated vapor andgenerating said first signal if a target material is detected.
 45. Theportable explosive detection screening system of claim 44 wherein saidsystem further includes a control and data processing means whichfurther comprises:a digital computer with a stored digital program whichis responsible for the control of the system; and a process controlmodule which is an interface between said digital computer and saidinterface control unit, said preconcentrator control unit and saidcontrol unit.
 46. The portable explosive detection screening system ofclaim 45 wherein said stored digital program is operable to control aplurality of processes including a self diagnostic and self calibrationprocesses, control of said sample collection, and processing ofcollected data from said detection means.
 47. A method for the detectionof concealed explosive chemical agents and other controlled substancessuch as drugs or narcotics by detecting their vapor or particulateemissions, said method comprising the steps of:(a) gathering a samplevolume of air from a specific area on a person or object, to collect anyvapor or particulate emissions from said person or object; (b)collecting vapor and the particulates in said sample volume of air witha sample collection means, said sample collection means including aparticulate collector for collecting and vaporizing said particulates;(c) concentrating said vapor or vapor subsequently emitted by saidcollected particulates by first adsorbing and secondly desorpting saidconcentrated vapor or vapors which emanated from said particulate; and(d) detecting said vapor desorbed from said second means for desorption.48. The method for the detection of concealed explosives according toclaim 47 wherein said collecting step further comprises drawing saidvolume of air to said concentrating means by means of a suction fan. 49.The method for the detection of concealed explosives according to claim48 wherein the desorbing of concentrated vapors includes the stepsofheating said adsorbed vapors to a predetermined desorbing temperature;and sweeping said vapors with an inert gas.
 50. The method for thedetection of concealed explosives according to claim 49 wherein saidstep of detecting further includes chemically analyzing said vapors. 51.The method for the detection of concealed explosives according to claim50 which further includes a step of controlling the collection andprocessing of data with a digital computer which utilizes a storedprogram.
 52. The method for the detection of concealed explosivesaccording to claim 49 which further includes a concentrating step whichthermally cleans residue from said adsorption and desorption with athermal cleaning step.
 53. The method for the detection of concealedexplosives according to claim 52 wherein said thermal cleaning comprisesthe steps of:heating said residue to a predetermined temperature tovaporize same; and sweeping said heated and vaporized residue to theambient environment.
 54. The method for the detection of concealedexplosives according to claim 48 wherein said step of detecting includessweeping said vapors and inert gas into a detection means.